WASHINGTON — The Army on Monday dropped sexual assault charges against a general whose trial has riveted the US military, allowing him to plead to lesser counts.
Under the plea deal, Brigadier General Jeffrey Sinclair acknowledged he ‘‘maltreated’’ a junior officer with whom he had a long affair and caused her emotional distress. In exchange, he will avoid a conviction on charges that would have required him to register as a sex offender and almost certainly would have resulted in prison time.
Sinclair’s sentence remains to be determined, although his attorneys said they have agreed to a side deal with the Army that would cap his punishment.
If the plea offer holds, it would represent the end of an exceptionally rare court-martial of an Army general — there have been only three such cases in the past 60 years — and an even rarer prosecution of a one-star commander on sexual-misconduct charges.
Sinclair’s voice halted Monday as he told the judge why he was pleading guilty to mistreating his accuser, an Army captain.
‘‘I failed her as a leader and as a mentor and caused harm to her emotional state,’’ Sinclair said, his voice catching as he read from a statement. He asked the judge for a break and took a drink of water before continuing to read.
‘‘I created a situation over time that caused her emotional harm,’’ Sinclair said, seated in his dress blue uniform. It was the first public show of regret or sadness for the 27-year veteran, who had betrayed little emotion in court hearings over the past year.
The judge Monday accepted Sinclair’s guilty pleas on several lesser charges, including having a relationship with a subordinate and committing adultery, which are crimes under military law. Sinclair admitted to abusing a government credit card he used while traveling to visit his mistress, using indecent language to demean female officers, and contacting the accuser after being told not to.
The married general pleaded guilty earlier this month to having improper relationships with three subordinate officers, including the captain.
The sentencing hearing for Sinclair, 51, the former deputy commander of the 82d Airborne Division, began Monday afternoon and was expected to last until at least Tuesday, the Associated Press reported. As many as two dozen witnesses could be called and Sinclair’s lawyer said he will either give a statement or testify.
The sentence cannot exceed terms in the agreement struck between defense lawyers and military attorneys over the weekend, which has not been made public. The punishment is expected to be far less severe than the maximum penalties of 21½ years in prison and dismissal from the Army.
Since the investigation began two years ago, the Sinclair case has caused endless legal and public relations headaches for the Army’s leadership.
The military has been grappling with an onslaught of sexual assault cases that have angered Congress and the White House and inflamed public opinion. Given that climate, Army leaders knew that how they handled the investigation of a general would be scrutinized closely.
The accusations against Sinclair were serious as well as sensational. The captain, who served on his staff in Iraq and Afghanistan, reported that she had carried on a torrid affair with the general for three years, having sex in two war zones and four countries.
But she reported the relationship to commanders after she said he twice forced her to perform oral sex. She also charged that he had once threatened to kill her and her family if she revealed the affair. The Washington Post generally does not name alleged sex-crime victims.
Sinclair defended himself vigorously after he was charged by the Army, hiring a high-priced team of civilian defense attorneys and a public relations firm.
Through his attorneys, he admitted the adulterous relationship but denied sexually assaulting or threatening the captain. His lawyers said the woman made up details to punish him for refusing to divorce his wife.
There were holes in the accuser’s story. E-mails and text messages introduced in court showed that she remained enamored with the general long after she asserted he had assaulted her.
She also gave conflicting accounts to other witnesses of whether the general had abused her, as well as about other important details in the case. In recent months, according to court filings, even prosecutors had concluded that she had credibility problems as they debated whether to accept a plea offer from Sinclair.
After Sinclair’s plea Monday, prosecutors opened the sentencing phase by calling the accuser back to the stand. She remains on active duty and was granted an immunity deal with prosecutors in exchange for testimony.
She said her career has suffered because she constantly worries her supervisors are talking about her behind her back and trying to undermine her.
‘‘I'm very guarded now. I have a hard time trusting people. I have a very hard time feeling safe,’’ said the woman.